EP 1985555 A (CROWN PACKAGING TECHNOLOGY INC) 29.10.2008 (also filed by the applicants) describes an earlier version of such a bag-in-can aerosol having a bag connected to a spout arrangement, which is then inserted into an aerosol can body. This patent application describes the advantages associated with using a bag-on-spout system as opposed to the conventional bag-on-valve systems and the use of a spout having a tubular section (to accommodate a preferred valve cup and valve) and a fish-tail sealing section (to provide a good seal between the spout and the bag). Although a plastic spout made from for example polypropylene (PP), as described in this application, is inexpensive, flexible, water resistant and can be easily heat sealed to the bag material, the inventor found that this arrangement did not provide sufficient barrier to the propellant (such as compressed gas or air) and the product filled into the bag (for example shave gel) still tended to pre-foam, which was unacceptable to both the customer (who filled the product into the bag) and the end user.
The fish-tail sealing section allowed a good seal to be provided between the spout and the bag and was easy to manufacture from polypropylene (PP), for example, by injection moulding . However, the barrier properties provided by the plastic spout described in EP 1 985 555 was found to be insufficient. Therefore, the inventor looked at using alternative materials to enhance the gas barrier properties required by such sensitive products.
These included thermoforming the tubular section (cup) with a multilayer material having an ethylene vinyl alcohol (EVOH) middle layer and polypropylene (PP) outer layers, but again the gas barrier properties were insufficient. The inventor also tried loading the polypropylene (PP) with nano-flakes of clay to improve the gas barrier properties. However, even 25% clay loading, the most the inventor could use before the polypropylene (PP) became too stiff to crimp without splitting, was found to provide insufficient barrier.
Next, the inventor tried manufacturing the spout from a metallised polymer, as the polymer retained the advantageous sealing properties between the spout and the bag, whilst the layer of metal provided the best barrier. The plastic material used was chosen so that it could bond with commercially available laminate bag materials, which commonly use polypropylene (PP) and polyethylene (PE) sealing layers. However, the metallised layer was found to be vulnerable to damage, leaving bare polymer, for example polypropylene (PP) exposed and thus diminishing the barrier properties of the spout to unacceptable levels.
The inventors found that an all metal spout provided the best barrier properties, but it was difficult to obtain a good seal between the all-metal spout and the bag. Therefore, the inventors tried producing the main body of the spout using conventional polymer coated steel, onto which a plastic fish-tail sealing section was moulded by insert moulding. The polymer coating on the steel provided a good bond with the plastic fish-tail sealing section, which was then heat sealed to the bag, providing a good seal with the bag. This arrangement was tested by filling the bag with shaving gel and then dispensing the shaving gel from a filled and pressurised aerosol can. The shaving gel was dispensed from the aerosol can as a smooth, clear gel with no pre-foaming.